DNA Replication: When lambda infected E. coli is gently lysed a major fraction of the phage DNA is found as a membrane-bound fast sedimenting species. EcoR1 digestion of such material yields two fractions. The first has normal DNA sedimentation properties while the second still sediments as a fast species and is greatly enriched for fragments bearing replication forks. We plan to investigate this system in detail and to map the points of membrane attachment. DNA Recombination: We wish to find conditions and to develop techniques which will allow us to study (by electron microscopy) recombinational intermediates which still have the enzymatic machinery attached.